Abstract: The disclosure relates to control and audio manipulation of a digital audio signal by a user manipulable rotary control. The disclosure is specifically applicable to manipulation of a digital audio signal by disc jockeys (DJs). A magnet and corresponding sensor are used to obtain rotational state information from the turning of the user manipulable rotary control. This rotational state information is used to manipulate a digital audio signal. Manipulation of the digital audio includes forward and backward motion as well as a “scratch effect”. Rotational state information obtained from rotating magnet includes the possibility of absolute rotation position as well as relative rotational position, or rotational direction.

Abstract: A device for playing back a music or video source such as a digital audio tape recorder, Compact Disc, Laser Vision Disc, video tape recorder, television and FM broadcasting and analog records comprises means responsive to control information supplied from a music or video source device for controlling an externally controllable electrical or electronic musical instrument so as to perform the musical instrument automatically in synchronism with playback of the source device. An electrical or electronic musical instrument is performed automatically in synchronism with playback of a source so that a reproduction atmosphere which cannot be obtained by mere playback of the source can be created.